8 Properties of cement
In Construction, cement serves as a binding cloth to keep other substances together. It is a first-class powder, made from a aggregate of limestone, clay, and other minerals, that hardens while mixed with water. Here are some of its properties
8 Physical Properties of Cement
During the manufacture of cement, manufacturers typically impose strict limits on the chemical composition and certain physical properties of the material. They conduct regular tests on the cement, either on the hardened cement paste or on concrete produced from the cement, to ensure that the quality remains within specified limits. Here is 8 Properties of Cement,
1.) Fineness
Is one of the essential physical homes of cement. Fineness affects the rate of hydration: the finer the cement, the faster strength development takes place. The effects of greater fineness on strength are particularly noticeable during the first 7 days. Also, as fineness increases, the amount of water required for a constant slump concrete decreases, to the limits reached by the higher ranges of fineness in high-early-strength cement.
2.) Soundness
Testing the ability of a hardened cement paste to maintain its volume after setting assesses a physical property known as soundness. Excessive hard-burned free lime or magnesia in the cement typically causes the lack of soundness.
3.) Setting time
An essential characteristic of cement that requires regulation is its capacity to keep concrete in a plastic state for a sufficient duration, allowing the completion of finishing operations. In practical circumstances, the length of time that a concrete mixture will remain plastic is usually more dependent on the amount of mixing water used and the atmospheric temperature. Rather than focusing on the setting time of the cement.
4.) False set
After mixing the concrete, it loses plasticity, typically without significant heat generation. Further mixing usually restores plasticity without the need for additional water. The use of chemical admixtures can be beneficial in delaying the occurrence of false set, which is the rapid development of rigidity in freshly mixed Portland cement paste, mortar, or concrete without the evolution of significant heat.
5.) Compressive Strength
The most crucial property of cement developed in a concrete mixture is compressive strength. Compressive strength is assessed through tests on 2-inch (50-mm) mortar cubes, using standard sand. Strength tests conducted at different ages or time intervals reveal the strength-producing characteristics of the cement. However, Relying solely on these tests for accurately predicting concrete strengths is not advisable, given the multitude of variables that can arise in different concrete mixtures. To accurately determine the compressive strength of concrete, one should conduct tests on samples made with the precise ingredients intended for the specific application.
6.) Heat of hydration
It is the warmth generated due to the chemical reaction between cement and water. The quantity and rate of warmth generated depends on the chemical composition of the cement. Fineness of the cement and the temperature during hydration. In some systems with massive mass, the charge and amount of warmth generated are large. If the generated heat is not swiftly dissipated, it can lead to an undesired increase in temperature, potentially causing thermal expansion. A subsequent drop in temperature may then create undesirable stresses in the structure.In cold weather, an increase in temperature may benefit by helping to maintain favorable curing conditions. The table illustrates the estimated heat generated during the initial seven days for each of the five cement types. Type 1 or normal Portland cement set at 100 percent as a reference.
7.) Specific Gravity
Its is a Portland cement is generally about 3.15. Cements made from materials other than limestone and clay may vary somewhat from the above value. Specific gravity is not an indication of the quality of the cement. It is employed in determining the proportions for mix design.
8.) Workability
The workability of cement refers to how easy it is to mix, place, and compact. This is an important property, especially for construction workers who need to shape the cement into specific forms.
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